1. Field of the Invention
The present invention relates to a speech recognition apparatus used in a vehicle, which apparatus operates to replace manual operations normally carried out by a driver. More particularly, this invention relates to a speech recognition apparatus which discriminates commands from a driver seat and a passenger seat and enhances the rate of speech recognition in a noisy vehicle room to thereby improve the reliability of the apparatus.
2. Description of the Related Art
A conventional speech recognition apparatus includes a microphone, speech recognition means for comparing an unknown speech pattern, formed by digital electrical signals converted from command voice signals from the microphone, with a registered speech pattern to recognize a speech, and various audio equipment controlled in accordance with the command recognized by the speech recognition means.
In the conventional speech recognition apparatus, when a driver at a driving seat in a vehicle gives the microphone a command of "AUDIO ON" or "AUDIO OFF", the speech recognition means recognizes the command of "AUDIO ON" or "AUDIO OFF" and causes the various equipment to be turned ON or OFF, respectively.
Therefore, the driver does not need to let go of the steering wheel while driving, or to be forced to look away from the road while traveling, to manipulate the various audio equipment.
Also, this speech recognition apparatus also obeys similar commands from a passenger seat, (see, for example, Japanese Unexamined Patent Publication (Kokai) No. 2-77799, No. 2-184898, No. 63-56698). Nevertheless, in the above speech recognition apparatus, since, for example, wipers, and rear view mirrors etc., of the vehicle can be also controlled by commands from the passenger seat, a problem arises in that such important manipulations can be performed by commands from the passenger seat, although not desired by the driver.
Further, although an improvement in the speech recognition rate is desired in the conventional speech recognition apparatus, when used in a vehicle a problem arises in that a wide variety of noise from outside of the vehicle causes a deterioration of the speech recognition rate. To resolve the above problems, if the microphone is given a strong directivity and is thus susceptible only to voice commands from the driving seat, to thereby eliminate outside noise, the desired speech recognition cannot be performed even when there is only a slight difference in the position of the driving seat, and further, the speech recognition from the passenger seat cannot be performed at all, due to the strong directivity of the microphone.